Preparation of radiation cured solid electrolytes and electrochemical devices employing the same

ABSTRACT

A method is described for forming a solid electrolyte comprising a polymeric network structure containing an ionically conducting liquid for use in solid state electrochemical cells which comprises forming a mixture of a crosslinkable polysiloxane or a crosslinkable polyethylene oxide, an ionically conducting liquid, and an ionizable ammonium or alkali metal salt, and subjecting said mixture to actinic radiation to thereby crosslink said crosslinkable polysiloxane or crosslinkable polyethylene oxide to form a solid matrix through which said ionically conducting liquid interpenetrates to provide continuous paths of high conductivity in all directions throughout said matrix.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. Application Ser. No.326,574, filed March 21, 1989 now abandoned which is a continuation ofApplication Ser. No. 173,385, filed March 25, 1988, now U.S. Pat. No.4,830,939 which is a continuation-in-part of U.S. Application Ser. No.115,492, filed Oct. 30, 1987 now abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to the manufacture of solid stateelectrochemical devices and, more particularly, solid stateelectrochemical devices in which the electrolyte is a polymeric networkinterpenetrated by an ionically conducting liquid phase.

Solid state electrochemical devices are the subject of intenseinvestigation and development. They are described extensively in thepatent literature. See, for example, U.S. Pat. No. 4,303,748 to Armand;4,589,197 to North; 4,547,440 to Hooper et al. and 4,228,226 toChristiansen. These cells are typically constructed of an alkali metalfoil anode, an ionically conducting polymeric electrolyte containing anionizable alkali metal salt, and a finely divided transition metal oxideas a cathode.

Ballard et al., U.S. Pat. No. 4,822,761 teaches an electrochemical cellwhich comprises a conductive anode and cathode capable of mutualelectrochemical reaction and separated by a solid electrolyte whichcomprises a matrix of sheets of atoms having side chains linked to thesheets, which side chains comprise polar groups free from activehydrogen atoms; a polar aprotic solvent dispersed in the matrix; and ahighly ionized ammonium or alkali metal salt.

Bauer et al., U.S. Pat. No. 4,654,279, describes a cell in which theelectrolyte is a two phase interpenetrating network of a mechanicallysupporting phase of a continuous network of a crosslinked polymer and aninterpenetrating conducting liquid polymer phase comprising an alkalimetal salt of a complexing liquid polymer which provides continuouspaths of high conductivity throughout the matrix. In one embodiment, aliquid complex of a lithium salt and polyethylene oxide is supported byan epoxy, a polymethacrylate, or a polyacrylonitrile matrix.

The network is formed by preparing a solution of the metal salt, thesalt-complexing liquid polymer, and the monomer for the crosslinkedsupporting phase in a polar solvent. The solvent is evaporated to form adry layer of a mixture of the remaining materials. The dry layer is thencured.

Le Mehaute et al., U.S. Pat. No. 4,556,614, discloses a solidelectrolyte for an electrochemical cell in which a salt complexingpolymer is mixed with a miscible and crosslinkable second polymer. Thefunction of the second polymer is to maintain the complexing polymer ina more highly conductive amorphous state. The is accomplished by forminga solution of the two polymers and an ionizable salt in a solvent,evaporating the solvent, and crosslinking the second polymer. The secondpolymer is crosslinked by radiation.

Andre et al., U.S. Pat. No. 4,357,601, generally relates to crosslinkedpolymeric electrolytes containing heteroatoms. The compositionsdescribed in the patent are chemically crosslinked, for example, throughthe reaction of a polyol and a polyisocyanate.

Xia et al., "Conductivities of Solid Polymer Electrolyte Complexes ofAlkali Salts with Polymers of Methoxypolyethyleneglycol Methacrylates,"Solid State Ionics, 14, (1984) 221-24 discloses solid polymericelectrolytes of ionizable salts and polymers prepared by polymerizingoligo-oxyethyl methacrylates. Reference is made at the end of the paperto experiments with radiation cross-linking. The polymers ranged from150,000 to 300,000 in molecular weight.

SUMMARY OF THE INVENTION

In accordance with the present invention the electrolyte is formed bypreparing a mixture of a liquid comprising a crosslinkable polysiloxaneor polyethylene oxide, a radiation inert ionically conducting liquid,and an ionizable ammonium or alkali metal salt, and curing the mixtureby exposing it to actinic radiation. In accordance with the preferredembodiments of the invention, the mixture contains a liquid monomeric orprepolymeric radiation polymerizable compound, a crosslinkablepolysiloxane or a crosslinkable polyethylene oxide, an ionicallyconducting liquid polyethylene oxide grafted polysiloxane and a lithiumsalt such as LiCF₃ SO₃. The mixture is cured by exposure to ultravioletor electron beam radiation. Where ultraviolet radiation is used, themixture will additionally include an ultraviolet initiator.

The radiation polymerizable electrolyte composition may be coated upon asupport or placed in a mold prior to exposure. Exposure of the mixtureproduces a polymerized or crosslinked (where trifunctional monomers areused) matrix which is interpenetrated in all directions by the radiationinert ionically conducting liquid phase. In accordance with the mosttypical embodiments of the invention, the radiation polymerizablecompounds are preferably low molecular weight polyethylenicallyunsaturated compounds and still more preferably compounds having atleast one heteroatom in the molecule which is capable of forming donoracceptor bonds with an alkali metal cation and having at least twoterminal polymerizable ethylenically unsaturated moieties. Whenpolymerized, these compounds form an ionically conductive matrix. Theradiation inert liquid is preferably an ionically conductive liquid or aliquid having heteroatoms capable of forming donor acceptor bonds withalkali metal cations. Most preferably, the ionically conducting liquidis a polyethylene oxide grafted polysiloxane. The liquid is free tointerpenetrate the matrix in a 3-dimensional fashion to providecontinuous paths of conductivity in all directions throughout thematrix.

The method of the present invention can be used to manufacture anode andcathode half elements as well as electrochemical cells. Anode halfelements are prepared by coating the radiation polymerizable electrolytecomposition described above on an appropriate anodic material such aslithium metal on nickel or copper foil; and conveying the coated foilmember past a radiation source. After exposure, the foil emerges withthe ion conductive network adhered to its surface. This not onlyprovides intimate contact between the foil and the electrolyte but italso protects the underlying foil surface from damage during subsequentmanufacturing operations in which it is assembled with the cathodeelement.

In accordance with one method of the present invention, a method forproviding a cathode half element is provided. In this method, a mixtureof an active cathode material, an electronic conductor, a liquidmonomeric or prepolymeric radiation polymerizable polyethylenicallyunsaturated compound, a radiation inert, ionically conducting liquid,and optionally an ionizable alkali metal salt is prepared; this mixtureis coated on a foil member which functions as a current collector, andexposed to actinic radiation to polymerize the polyethylenicallyunsaturated compound. In some cases the ionizable alkali metal salt maybe omitted from the radiation polymerizable cathode composition tofacilitate coating. An excess of an ionically conductive salt may beincorporated in the electrolyte layer which subsequently diffuses intothe cathode layer when the cell is assembled.

The present invention is also useful in manufacturing a completedelectrochemical cell. In accordance with one method, anode and cathodehalf elements prepared by any process may be assembled with a layer of aradiation polymerizable electrolyte composition in accordance with thepresent invention therebetween, and the assembly may be exposed toradiation to cure the electrolyte layer and thereby adhere the anode andcathode half elements together.

Other methods may also be used. For example, cured anode and cathodehalf elements prepared in accordance with the present invention may beassembled using heat and pressure in a conventional manner.Alternatively, a cured anode or cathode half element prepared by anyprocess may be assembled with an uncured anode or cathode half elementin accordance with the present invention and the assembly may be exposedto radiation to adhere the two elements together. In accordance withstill another method of the present invention, uncured anode and cathodehalf elements carrying radiation polymerizable compositions inaccordance with the present invention may be assembled and the assemblymay be exposed to radiation to cure the elements and at the same timesecure the cell together. It will also be apparent that a foil membermay be coated with a radiation polymerizable electrolyte and cathodecompositions in accordance with the present invention, assembled withthe foil member forming the anode or the current collector for thecathode, and this assembly may be cured.

Accordingly, one manifestation of the present invention is a method forforming an interpenetrating polymeric network containing a liquidelectrolyte for use in solid state electrochemical cells which comprisesforming a mixture of a liquid, monomeric or prepolymeric radiationpolymerizable compound, a crosslinkable polysiloxane or a crosslinkablepolyethylene oxide, a radiation inert ionically conducting liquid, andan ionizable ammonium or alkali metal salt; subjecting said mixture toactinic radiation to thereby crosslink said radiation polymerizablecompound and thereby form a solid matrix containing said ionicallyconducting liquid.

Another manifestation of the present invention is a method for formingan anode half element which comprises coating an anodic metal foilmember with a mixture which includes the aforementioned radiationpolymerizable material, a crosslinkable polysiloxane or a crosslinkablepolyethylene oxide, a radiation inert ionically conducting liquid, andan ionizable alkali metal salt; and subjecting said mixture to actinicradiation to thereby crosslink said radiation polymerizable compound andform a solid matrix containing said ionically conducting liquid.

The present invention also provides a method for forming a cathode halfelement which comprises forming a mixture of an active cathode material,an electronic conductor, a liquid monomeric or prepolymeric radiationpolymerizable compound, a crosslinkable polysiloxane or a crosslinkablepolyethylene oxide, a radiation inert ionically conducting liquid, andoptionally, an ionizable ammonium or alkali metal salt; coating saidmixture on a metal foil member; and exposing said mixture to radiationto cure said radiation polymerizable polyethylenically unsaturatedcompound and thereby form a polymeric network interpenetrated by saidionically conducting liquid.

A further method in accordance with the present invention is a methodfor forming an electrochemical cell which comprises assembling an anodeand a cathode half element having a radiation polymerizable electrolytecomposition therebetween including a liquid monomeric or prepolymericradiation polymerizable compound, a crosslinkable polysiloxane or acrosslinkable polyethylene oxide, a radiation inert ionically conductingliquid, and an ionizable ammonium or alkali metal salt; and exposing theassembly to radiation to polymerize the radiation polymerizable compoundand thereby secure the anode and cathode half elements together via apolymeric network interpenetrated by said ionically conducting liquid.

Still another method in accordance with the present invention comprisescoating an anodic metal foil member with a radiation polymerizableelectrolyte composition including a liquid monomeric or prepolymericradiation polymerizable compound, a crosslinkable polysiloxane or acrosslinkable polyethylene oxide, a radiation inert ionically conductingliquid, and an ionizable ammonium or alkali metal salt; overcoating saidradiation polymerizable electrolyte composition with a radiationpolymerizable cathode composition including an active cathode material,an electronic conductor, a liquid monomeric or prepolymeric radiationpolymerizable compound, a radiation inert ionically conducting liquid,and optionally an ionizable ammonium or alkali metal salt; overlayingsaid radiation polymerizable cathode composition with a foil memberfunctioning as a current collector for said cathode, and exposing thelaminate so obtained to radiation to polymerize the radiationpolymerizable compound and thereby form an electrochemical cell. Thisprocess may be reversed in accordance with which the current collectorfor the cathode may be coated with a radiation polymerizable cathodecomposition which is overcoated with the radiation polymerizableelectrolyte composition described above. This material is assembled withan anodic metal foil member and exposed to radiation.

DETAILED DESCRIPTION OF THE INVENTION

The network which is interpenetrated by the ionically conducting liquidin the present invention may be a conductive matrix in which case it isformed from organic monomers or polymers containing heteroatoms capableof forming donor acceptor bonds with an alkali metal cation; or anon-conductive supportive matrix in which case the aforesaid heteroatomsare not present. Polymeric materials containing, e.g., silicon andoxygen atoms in the chain, such as polysiloxanes inherently have low Tgand higher conductivity than polymers previously used. These propertiesallow the supporting matrix to have increased conductivity at lowtemperatures. The preferred monomers or prepolymers are described below.

Polyethylenically unsaturated monomeric or prepolymonomeric materialsuseful in the present invention are preferably compounds having at leastone, and more preferably a plurality, of heteroatoms (particularlyoxygen and/or nitrogen atoms) capable of forming donor acceptor bondswith an alkali metal cation and are terminated by radiationpolymerizable moieties. The polyethylene unsaturated compounds include arepeating unit selected from ##STR1## where R' is hydrogen or a loweralkyl group. These compounds yield a conductive supportive matrix. Morespecifically they are preferably low molecular weight oligomers of theformulae (I)-(III) below ##STR2## where n is about 3 to 50 and R ishydrogen or a C1-C3 alkyl group, which are terminated by ethylenicallyunsaturated moieties or glycidyl moieties represented by A.

A particularly useful group of radiation polymerizable compounds isobtained by reacting a polyethylene glycol with acrylic or methacrylicacid. Also useful in the present invention are radiation curablematerials such as polyethylene oxide; polysiloxanes, e.g., polyethyleneoxide grafted polysiloxanes; acrylated epoxies, e.g., Bisphenol A epoxydiacrylate; polyester acrylates, such as Uvithane ZL-1178, an acrylatefunctionalized polyurethane available from Morton Thiokol ChemicalCompany; copolymers of glycidyl ethers and acrylates or a vinyl compoundsuch as N-vinylpyrrolidone. The latter provides a non-conductive matrix.In selecting these monomers, monomers are selected which do notadversely react with the anodic metal which tends to be highly reactive.For example, halogenated monomers such as vinyl chloride are preferablyavoided. Monomers which react with the anodic metal, but which reactwith it very slowly may be used, but are not desirable.

Preferably, the radiation polymerizable polyethylenically unsaturatedcompounds have a molecular weight of about 200 to 2,000 and morepreferably 200 to 800. Still more preferably they are liquids attemperatures less than 30° C. Examples of radiation curable materialsinclude polyethylene glycol-300 diacrylate (average PEO molecular weightabout 300), polyethylene glycol-480 diacrylate (average PEO molecularweight about 480) and the corresponding methacrylates.

It may be desirable to include a radiation curable comonomer in thecomposition to reduce the glass transition temperature and improveconductivity of the polymer. Any suitable monoacrylate such astetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate,methoxypolyethylene glycol monomethacrylate, 2-ethoxyethyl acrylate,2-methoxyethyl acrylate or cyclohexyl methacrylate may be used for thispurpose. Triacrylates such as TMPTA, trimethylolpropane ethoxylatedtriacrylate (TMPEOTA) or trimethylolpropane propoxy triacrylate may beused to introduce crosslinking of the polymer. There should besufficient rigidity in the layers maintaining separation of the anodeand cathode that the cell does not discharge with handling.Monoacrylates may be used in an amount of about 5 to 50% by weight basedon the total amount of radiation polymerizable material. Thetriacrylates are used in amounts of about 2 to 30% by weight on the samebasis.

The supportive matrix may be formed in whole or in part from theradiation curable compound. As illustrated in Examples 12 and 13 amountsof higher molecular weight PEO may be added to the composition.

The radiation inert liquids which form the ionically conductive liquidinterpenetrating phase can be any low volatile material which remainsliquid upon exposure to radiation. Low volatility simplifies manufactureand improves shelf life. Preferably, these materials are characterizedby a boiling point greater than about 80° C. Representative examples arepropylene carbonate, γ-butryrolactone, 1,3-dioxolane, and2-methyltetrahydrofuran. Less polar solvents having heteroatoms capableof bonding alkali metal cations are also useful. Polyethylene glycoldimethyl ether (PEGDME) is a preferred example. Glymes such astetraglyme, hexaglyme, and heptaglyme are also desirable solvents.Liquid polysiloxanes, e.g., polyethylene oxide grafted polysilanes areparticularly useful in the present invention for the preparation of asemi-interpenetrating polymeric network wherein the liquid polyethyleneoxide grafted polysiloxane is trapped within the matrix, therebyincreasing the structural strength and integrity of the matrix.

The radiation curable mixture of this invention contains at least 45% byweight of the radiation inert liquid and about 20 to 55% by weight andpreferably 25 to 40% by weight of the radiation polymerizable compound.The exact amount of the radiation polymerizable compound and theradiation inert liquid should be adjusted to provide the optimumcombination of strength and conductivity for the particular application.As a general rule, if the mixture contains less than about 20% of thepolymerizable compound, the electrolyte will be too weak to maintainelectrode separation. If the mixture contains greater than about 55%polymerizable material, the electrolyte exhibits poor conductivity. Inthose cases in which the electrolyte composition itself or an electrodecomposition containing the electrolyte is coated on a supporting member,such as a current collector or an electrode half element, theelectrolyte often is not required to have the structural integrity of afree standing film. In those applications it is permissible andadvantageous to use a higher quantity of the radiation inert liquidbecause greater conductivity can be achieved, for example it isadvantageous to use about 70 to 80% of the radiation inert liquid.

Ionizable alkaline metal salts useful in this invention include thosesalts conventionally used in solid state electrochemical cells.Representative examples are sodium, lithium, and ammonium salts of lessmobile anions of weak bases having a large anionic radius. Examples maybe selected from the group consisting of I⁻, Br⁻, SCN⁻, C10₄ ⁻, BF₄ ⁻,PF₆ ⁻, AsF₆ ⁻, CF₃ COO⁻, CF₃ SO₃ ⁻, etc. Specific examples are LiClO₄,NaClO₄, LiF₃ CSO₃, and LiBF₄.

The salt may be used up to an amount which does not exceed itssolubility limit in the electrolyte. The amount will therefore vary withthe nature of the radiation polymerizable material and the radiationinert liquid solvent. As a general rule, the maximum amount of saltwithin its solubility limit should be used to maximize the ionicconductivity of the electrolyte. In most applications about 10 to 60parts salt is used per 100 parts of radiation inert liquid phase.

The method of the present invention can be used to produce free standingfilms or electrode half elements. To produce a free standing film, theradiation curable mixture may be poured into a mold or coated onto asurface having a release characteristic such as PTFE and cured byexposure to actinic radiation. The electrolyte film thickness can varybut films about 15 to 100 microns thick and preferably 20 to 50 micronsthick are useful in many applications. The obtained film can beassembled with cathode and anode half elements prepared by the processesdisclosed herein or prepared by other processes and laminated under heatand pressure. A conductive adhesive my be used if necessary.

Anode half elements are obtained by coating a foil of the anode metalwith the radiation curable composition and exposing to radiation. Atypical foil is lithium foil or lithium coated foil such as nickel orcopper foil having a layer of lithium deposited on its surface. Lithiumis preferred because it is very electropositive and light in weight. Theradiation curable composition may be coated in any manner. Suitabletechniques are rod coating, roll coating, blade coating, etc.

Coating compositions for cathode half elements include particles of theinsertion compound and an electrically conductive material. The cathodehalf element is obtained by coating a foil member such as nickel foilwith the aforesaid composition in a thickness of about 10 to 100 micronsand preferably about 30 to 60 microns, and curing. The cathodecomposition may be coated by any of the techniques discussed previously,but it is particularly desirable to design an extrudable cathodecomposition. The radiation curable composition used in the presentinvention functions as a dispersing medium for the cathode materials. Atypical coating formulation for a cathode half element may contain about50 to 80 parts of the insertion compound, about 2 to 15 parts of aconductive particle such as carbon black and about 15 to 50 parts of theradiation curable composition described above. As previously indicatedthe ionizable salt can be omitted from the cathode composition if it isable to diffuse into the cathodes after assembly with the electrolyte.It may enhance the extrudability of the cathode composition to omit thesalt and rely upon its diffusion within the electrochemical cell to fillthe cathode. Also, for extrudability, it may be desirable to use ahigher amount of ionically conductive liquid in the cathode compositionand less in the electrolyte composition and to rely upon diffusion tobalance the concentration when the cell is formed.

Insertion compounds and electronically conductive materials useful inthe present invention are well known in the art. Representative examplesof insertion compounds are V₆ O₁₃, MnO₂, MnO₂ and TiS₂. Other examplescan be found in the aforementioned references. A conductive material iscarbon black. Certain conductive polymers (which are characterized by aconjugated network of double bonds) like polypyrol and polyacetyline mayalso be used for this purpose.

In accordance with a further embodiment of the invention, the compositecathodic particles described in U.S. Pat. No. 4,576,883 to Hope can bedispersed in the curable composition and coated on a metal foil memberas described above.

In preparing the coating compositions for the cathode half element, asmall amount of a volatile solvent and a dispersing agent such aslecithin can be added to disperse the cathodic material in thecomposition and produce a composition having good coatingcharacteristics.

The term "actinic radiation" as used herein includes the entireelectromagnetic spectrum and electron beam and gamma radiation. It isanticipated, however, based on availability of radiation sources andsimplicity of equipment that electron beam and ultraviolet radiationwill be used most often. Electron beam and gamma radiation areadvantageous because they do not require the presence of aphotoinitiator. When a photoinitiator is required, for example whenusing ultraviolet radiation, initiators selected from among conventionalphotoinitiators may be used. When using electron beam, the beampotential must be sufficiently high to penetrate the electrode layer,the anode or cathode half element, or the cell itself depending uponwhich manufacturing technique is adopted. Voltages of 175 to 300 KV aregenerally useful. The beam dosage and the speed with which the elementtraverses the beam are adjusted to control the degree of crosslinking inan otherwise known manner.

It will be apparent from the foregoing description that the methods ofthe present invention can also be used to manufacture a completeelectrochemical cell. Cured anode and cathode half elements prepared asabove can be laminated together under heat and pressure in an otherwiseknown manner. Alternatively, however, the electrochemical device can beassembled "wet" and then cured in situ. For example, in accordance withthe present invention, a lithium coated foil member can be coated withthe radiation polymerizable electrolyte composition and overcoated withthe cathode coating composition described previously; or a nickel foilmember can be coated with the cathode coating composition describedpreviously and overcoated with the radiation polymerizable electrolytecomposition. These structures can be cured by exposure to electron beamor another source of actinic radiation and the current collector oranodic member can be assembled with it. In another embodiment the foilmembers associated with both the anode and the cathode half elements maybe assembled to form the completed cell and this structure may be curedby electron beam as shown in Example 11.

Thus, in one method a current collector such as a nickel foil member maybe coated with a radiation polymerizable cathode composition inaccordance with the present invention. This structure is overcoated witha layer of the radiation polymerizable electrolyte composition describedabove and assembled with an anodic member such as a lithium foil memberor a lithium coated nickel or aluminum member. This assembly may becured by exposure to electron beam to provide an electrochemical cell.The cured electrolyte and cathode compositions adhere to one another aswell as to the metal foil members associated with the anode and cathode.

The process described above can also be reversed. An anodic metal foilmember such as lithium coated metal foil can be coated with theradiation polymerizable electrolyte composition described above. Theradiation polymerizable cathode composition is coated over theelectrolyte composition and a nickel foil member or other currentcollector is applied to the cathode layer. The assembly is subjected toelectron beam radiation to produce an electrochemical cell in accordancewith the present invention.

In another process, the anodic foil member or the current collector maybe coated with the appropriate cathode or electrolyte composition andthat composition may be cured (e.g., by exposure to radiation when it isradiation curable). The cured composition may be overcoated with theother of the electrolyte or cathode composition thereafter, and theovercoating may be cured or the remaining anodic foil member or currentcollector may be laminated and then the overcoating cured.

Other methods for manufacturing anodes, cathodes, or electrochemicalcells will also be evident which utilize the radiation polymerizableelectrolyte composition of the present invention. It has been found thatthis composition is effective in bonding the anode and cathode elementstogether and, at the same time, provides a polymeric matrixinterpenetrated by an ionically conductive liquid.

The invention is illustrated in more detail by way of the followingnon-limiting examples.

EXAMPLE 1

1g of poly(ethylene glycol) diacrylate, M.W. 300, 1g of poly(ethyleneglycol) dimethyl ether, M.W. 400, and 0.3g of lithium trifluoromethanesulfonate were mixed together. Benzophenone, 0.1g was then added and themixture, as a thin layer, poured into an aluminum weighing dish. Thismixture was irradiated in an Argon atmosphere for 1 minute with GEF40/BLB blacklight, (output range from 300-420nm and output maximumslightly above 350nm). The exposure transformed the liquid mixture intoa flexible, opaque film with a dry feel. Its ionic conductivity is2.8×10⁻⁵ ohm⁻¹ cm⁻¹.

EXAMPLE 2

0.5g of poly(ethylene glycol) diacrylate, 0.5g of poly(ethylene glycol)diqlycidyl ether, lg of poly(ethylene glycol) dimethyl ether and 0.6g oflithium trifluoromethane sulfonate were mixed together, 0.1g ofbenzophenone was then added and then the mixture irradiated in analuminum weighing dish, using the same U.V. lamp as in Example 1. Theflexible, opaque film had an ionic conductivity of 2.7×10⁻⁵ ohm⁻¹ cm⁻¹.

EXAMPLE 3

2g of poly(ethylene glycol)diacrylate, avg. M.W. 300, 2g ofpoly(ethylene glycol)dimethyl ether, avg. M.W. 400, and 0.6g of lithiumtrifluoromethane sulfonate were mixed together. This mixture was thencoated on aluminum foil and irradiated by electron beam with 3 Megaradsat 20 ft/min. (Energy Science Inc.). This resulted in a clear andflexible dry film.

EXAMPLE 4

2g of UVITHANE ZL-1178. 2g of poly(ethylene glycol) dimethylether and0.6g of lithium trifluoromethane sulfonate were mixed together. UVITHANEZL-1178 is a diacrylate functionalized polyurethane with ether portionsbuilt up from poly(propylene glycol) from Morton Thiokol Chemical Co.This mixture was then coated on aluminum foil and irradiated by electronbeam with 3, 6, 9 and 12 MR (Megarads) at 20 ft/min.(fpm). This resultedin clear and flexible dry films.

EXAMPLE 5

Onto a sheet of industrial strength aluminum foil was coated with adrawdown bar a film of the following mixture:

    ______________________________________                                        Poly(ethylene glycol)diacrylate                                                                         2.0   g                                             (avg. M.W. of PEO 300)                                                        Poly(ethylene glycol) dimethyl ether                                                                    2.0   g                                             (avg. M.W. of PEO 400)                                                        Lithium trifluoromethane sulfonate                                                                      0.6   g                                             ______________________________________                                    

The coated foil was passed through the path of an electron beam emittingsource at a speed of 20 fpm. Doses of 3, 6, 9, and 12 MR were used. Inall four cases a polymer film cured onto the aluminum foil was obtained.The resulting ionic conductivities are on the order of 10⁻⁵ (ohm⁻¹cm⁻¹).

EXAMPLE 6

Onto a sheet of industrial strength aluminum foil was coated with adrawdown bar a film of the following mixture:

    ______________________________________                                        Poly(ethylene glycol)diacrylate                                                                         2.0   g                                             (avg. M.W. of PEO 300)                                                        Poly(ethylene glycol) dimethyl ether                                                                    1.0   g                                             (avg. M.W. of PEO 400)                                                        Lithium trifluoromethane sulfonate                                                                      0.1   g                                             Unitized V.sub.6 O.sub.13 particles                                                                     1.0   g                                             [70% V.sub.6 O.sub.13, 20% PEO (M.W. 400,000)                                 10% Shawinigan carbon prepared as                                             described in U.S. Pat. No. 4,576,883]                                         ______________________________________                                    

The coated aluminum foil was passed through the path of an electron beamemitting source at a speed of 20 fpm and dosage of 12 MR. A blackflexible polymer film on an aluminum was the result.

EXAMPLE 7

Onto a sheet of industrial strength aluminum foil was coated with adrawdown bar a film of the following mixture:

    ______________________________________                                        Poly(ethylene glycol)diacrylate                                                                        2.5    g                                             (avg. M.W. of PEO 300)                                                        Poly(ethylene glycol) dimethyl ether                                                                   2.8    g                                             (avg. M.W. of PEO 400)                                                        Uvithane ZL-1178         2.8    g                                             Lithium trifluoromethane sulfonate                                                                     0.84   g                                             Unitized V.sub.6 O.sub.13                                                                              3.0    g                                             ______________________________________                                    

The coated foil was passed through the path of an electron beam sourceat a speed of 20 fpm and a dose of 12 MR. This resulted in curing theliquid film into a flexible black polymer on aluminum foil.

EXAMPLE 8

Onto a sheet of industrial strength aluminum foil was coated with adrawdown bar a film of the following mixture which had been ground in aball mill to the desired particle size.

    ______________________________________                                        V.sub.6 O.sub.13         35     g                                             Lecithin                 0.75   g                                             Methylethyl ketone (MEK) 33     g                                             Heptaglyme               15     g                                             Carbon black             3.5    g                                             Polyethylene Glycol Diacrylate                                                                         15.    g                                             ______________________________________                                    

The solvent (MEK) was allowed to evaporate. The resulting film was thenpassed through the path of an electron beam source at a speed of 50 fpmand a dose of 12 Megarads. This gave a cured flexible black film usefulas a cathode half element.

EXAMPLE 9

A film was prepared as in Example 8 without curing. A mixture ofpre-polymer electrolyte as in Example 5 was then coated on top of it.This sample was then passed through the path of an electron beam sourceat a speed of 50 fpm and a dose of 12 MR. This gave a cured, glossyblack film which could be assembled with another foil member to be usedas an electrochemical device.

EXAMPLE 10

A coating was prepared and cured as in Example 8. A mixture ofpre-polymer electrolyte as in Example 5 was then coated on top of it.This sample was then passed through electron beam source at a speed of50 fpm and a dose of 3 MR. This gave a cured black film which could beassembled with another foil member for use as an electrochemical device.

EXAMPLE 11

The coatings were prepared as described in Example 9. The coatings werethen covered with nickel foil. This construction was then cured bypassage through an electron beam operating at 175 KV, a dosage of 6 MRand a speed of 20 fpm to provide an electrochemical device. Nickel foilwas selected merely to demonstrate that the electrode and electrolytecompositions could be cured by electron beam through the foil. Toprepare an electrochemical cell, the cathode composition of Example 8would be coated on a lithium foil member or a lithium coated member in adry room.

EXAMPLE 12

The radiation curable extrudable polymer electrolyte compositionscontaining polyethylene oxide (PEO), polyethylene glycol diacrylate,(PEG-DA), trimethylolpropane ethoxylated triacrylate (TMPEOTA), LiCF₃SO₃ and a suitable ionic conductive solvent such as tetraglyme orpropylene carbonate were made and extruded on aluminum foil using aBrabender extruder at 125° C. as shown in the Table below. The extrusionmixture was prepared as follows: First, the salt was dissolved in halfof the propylene carbonate. The PEO is dispersed in the other half ofthe propylene carbonate, then PEG-DA and TMPEOTA are added to themixture. The salt and the PEO compositions are mixed and the mixture ispoured into the input of the extruder.

                  TABLE                                                           ______________________________________                                                   Sample No. (wt. %)                                                 Compound     1      2          3    4                                         ______________________________________                                        PEG-DA (400) --     --         0.04 0.10                                      TMPEOTA      0.03   0.13       0.01 0.01                                      Tetraglyme   0.70   0.60       0.75 0.65                                      PEO          0.20   0.20       0.05 0.10                                      LiCF.sub.3 SO.sub.3                                                                        0.07   0.07       0.15 0.14                                      ______________________________________                                    

Samples 1-4 were then passed through the electron beam at 7.8 MR to giveflexible, opaque films about 1 to 5 mils thick having a conductivity of7×10⁻⁵ ohm⁻¹ cm⁻¹.

EXAMPLE 13

The following mixtures containing propylene carbonate (PC) were alsomade:

    ______________________________________                                                        Sample No. (wt. %)                                            Compound          PC-1   PC-2                                                 ______________________________________                                        PEG-DA            0.10   0.10                                                 TMPEOTA           0.01   0.01                                                 PC                0.65   0.65                                                 PEO               0.10   0.05                                                 LICF.sub.3 SO.sub.3                                                                             0.14   0.19                                                 ______________________________________                                    

The materials were extruded under the same conditions described inExample 13 and passed through the electron beam to give clear, flexiblefilms having a conductivity of 2×10⁻³ ohm⁻¹ cm⁻¹.

EXAMPLE 14

Cathode mixtures containing 50% V₆ O₁₃, 7% Shawinigan Black and 43% ofcompositions PC-1 and PC-2 from Example 13 were extruded onto nickle oraluminum foil under the same conditions as described above and cured byelectron beam at 7.8 MR.

EXAMPLE 15

Batteries were made as follows:

(1) Extruding the cathode composition of Example 14 on aluminum foil;

(2) Curing the cathode composition by electron beam as in Example 14;

(3) Extruding composition PC-2 from Example 13 on top of the curedcathode composition;

(4) Laminate with lithium foil;

(5) Passing the structure through an electron beam at 7.8 MR. Thelithium foil retained its property during this process.

EXAMPLE 16

Batteries were made as follows:

(1) Extruding the cathode composition of Example 14 on aluminum foil;

(2) Curing the cathode composition by electron beam as in Example 14;

(3) Extruding composition PC-2 from Example 13 on top of the curedcathode composition;

(4) Passing the coating through the electron beam at 7.8 MR;

(5) Laminating lithium foil to the laminate of step (4) by heat and/orpressure roll.

EXAMPLE 17

2g of Dow Corning elastomer DC7150-98 (polyethylene oxide graftedpolysiloxane), 2g propylene carbonate, and 0.66g of LiCF₃ SO₃ were mixedtogether to give a clear solution. This solution was coated on aluminumfoil and irradiated by electron beam with 5 Megarads at 20 ft./min. togive a clear flexible film having an ionic conductivity in the order of10⁻⁴ ohm⁻¹ cm⁻¹.

EXAMPLE 18

Example 17 was repeated resulting in a clear flexible film.

EXAMPLE 19

Example 17 was repeated except that polyethylene oxide dimethyl etherwas used in place of the propylene carbonate. The resulting solution wascoated on aluminum foil and irradiated by electron beam with doses of 5and 10 Megarads to give a clear flexible film.

EXAMPLE 20-22

In Examples 20-22, mixtures were prepared using the procedure of Example17 except that Dow Corning elastomer DC 7150-104 (a polyethylene oxidegrafted polysiloxane) was used in place of the Dow Corning elastomer DC7150-98. The resulting film from each of Examples 20-22 was a clearflexible film.

EXAMPLES 23-26

The following mixtures were prepared as shown below and each mixtureplaced in a separate aluminum weighing pan. Each Example containing 5%benzophenone as UV initiator was UV-cured to give an opaque film.

    ______________________________________                                                     Example No.                                                      Compound       23    24        25   26                                        ______________________________________                                        TMPTA.sup.1    --    --        0.1  --                                        PEG-DA.sup.2   0.5   1.0       0.4  --                                        LICF.sub.3 SO.sub.3                                                                          0.2   0.3        0.21                                                                               0.15                                     Tego Wet KL-245.sup.3                                                                        0.5   0.5       0.7  0.5                                       Siloxane.sup.4 --    --        --   0.5                                       ______________________________________                                         .sup.1 Trimethylolpropane triacrylate                                         .sup.2 Polyethylene glycol diacrylate                                         .sup.3 polyethylene oxide grafted polysiloxane, made by Goldschmidt AG        .sup.4 Bis(methacryloxypropyl) tetramethyldisixane                       

Having described the invention in detail and by reference to preferredembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of the appendedclaims.

What is claimed is:
 1. A method for forming a solid electrolytecomprising a polymeric network structure containing an ionicallyconducting liquid for use in solid state electrochemical cells whichcomprises forming a mixture of a crosslinkable polysiloxane or acrosslinkable polyethylene oxide, an ionically conducting liquid, and anionizable ammonium or alkali metal salt, and subjecting said mixture toactinic radiation to thereby crosslink said crosslinkable polysiloxaneor crosslinkable polyethylene oxide to form a solid matrix through whichsaid ionically conducting liquid interpenetrates to provide continuouspaths of high conductivity in all directions throughout said matrix. 2.The method of claim 1 wherein said mixture also contains a crosslinkablepolyethylenically unsaturated compound.
 3. The method of claim 2 whereinsaid crosslinkable polysiloxane is a polyethylene oxide graftedpolysiloxane.
 4. The method of claim 3 wherein said polyethylenicallyunsaturated compound including at least one heteroatom in the molecule.5. The method of claim 4 wherein said polyethylenically unsaturatedcompound includes a repeating unit selected from the group consisting of##STR3## where R' is hydrogen or a lower alkyl group.
 6. The method ofclaim 5 wherein said polyethylenically unsaturated compound isrepresented by the formulas I to III below, ##STR4## where n is about 3to 50 and R is hydrogen or a C₁ -C₃ alkyl group and A represents anethylenically unsaturated moiety or a glycidyl moiety.
 7. The method ofclaim 6 wherein said polyethylenically unsaturated compound is apolyethylene glycol modified to include terminal ethylenicallyunsaturated groups.
 8. The method of claim 7 wherein saidpolyethylenically unsaturated compound is polyethylene glycoldiacrylate, polyethylene glycol dimethacrylate, an acrylate functionizedpolyurethane, or polyethylene glycol diglycidyl ether.
 9. The method ofclaim 8 wherein said ionizable salt is a salt of a cation selected fromthe group consisting of lithium, sodium, potassium, and ammoniumcations; and an anion selected from the group consisting of I⁻, Br⁻,SCN⁻, ClO₄ ⁻, CFSO₃ ⁻, BF₄ ⁻, PF₆ ⁻, AsF₆ ⁻, and CF₃ COO⁻.
 10. Themethod of claim 9 wherein said ionizable salt is a lithium salt.
 11. Themethod of claim 10 wherein said lithium salt is LiCF₃ SO₃.
 12. Themethod of claim 1 wherein said ionically conducting liquid is selectedfrom the group consisting of polyethylene glycol dimethyl ether,propylene carbonate, gamma-butyrolactone, 1,3-dioxolane,2-methyltetrahydrofuran, tetraglyme, hexaglyme, and heptaglyme, andpolyethylene oxide grafted polysiloxane.
 13. The method of claim 12wherein said ionically conducting liquid is a polyethylene oxide graftedpolysiloxane.
 14. The method of claim 12 wherein said ionicallyconducting liquid is present in said mixture in an amount of at least45% by weight.
 15. The method of claim 12 wherein said ionicallyconducting liquid in present is said mixture in an amount of at least70% by weight.
 16. The method of claim 14 wherein said mixtureadditionally contains a radiation curable comonomer.
 17. The method ofclaim 15 wherein said radiation curable comonomer is trimethylolpropanetriacrylate, trimethylolpropane ethoxylated triacrylate ortrimethylolpropane propoxy triacrylate.
 18. A method for forming a solidelectrolyte comprising a polymeric network structure containing anionically conducting liquid for use in solid state electrochemical cellswhich comprises forming a mixture of a crosslinkable polyethylenicallyunsaturated compound, a crosslinkable polysiloxane or a crosslinkablepolyethylene oxide, an ionically conducting liquid polyethylene oxidegrafted polysiloxane, and LiCF₃ SO₃, said polyethylenically unsaturatedcompound being represented by the formulas ##STR5## where n is about 3to 50, R is hydrogen or a C₁ -C₃ alkyl group and A represents anethylenically unsaturated moity or a glycidyl moiety, and subjectingsaid mixture to actinic radiation to form a solid matrix through whichsaid ionically conducting, liquid polyethylene oxide graftedpolysiloxane interpenetrated to provide continuous paths of highconductivity in all directions.
 19. The method of claim 18 wherein saidpolyethylene oxide grafted polysiloxane is present in said mixture in anamount of at least 45% by weight.
 20. The method of claim 19 whereinsaid mixture additionally contains trimethylolpropane triacrylate,trimethylolpropane ethoxylated triacrylate or trimethylolpropanepropoxylated triacrylate.